1. Field of the Invention
This invention relates to a gas generating apparatus used for inflating an air bag such as one used for a safety apparatus for protection against collison, life bag, rubber boat, escape chute, etc. More particularly, this invention concerns a gas generating apparatus for inflating an air bag whereby any shortfall in the quantity of gas required for inflating the air bag can be overcome by replenishing the air bag with air.
2. Statement of the Prior Art
Conventionally, in a passenger car, a safety apparatus adapted to protect passengers against physical shock at the time of a collision comprises an air bag with a volume of 60 liters and a gas generating apparatus which inflates this air bag, the gas generating apparatus being filled either with an explosiver or a gas generating agent comprising similar constituents which is ignited and burnt at the time or a collision so as to immediately inflate the air bag with a gas generated thereby, thus protecting the driver from the effects of the collision, and preventing him from being seriously injured.
In such an apparatus, the quantity of gas generating agent required for inflating the air bag is between 70 and 100 g, and the total weight of the body of the gas generator is between 600 and 1100 g. With the above apparatus, the air bag is inflated merely by the generation of gas upon combustion of the gas generating agent; therefore, even an air bag with a 60-liter volume uses from 70 to 100 g of the generated gas, which is a relatively large amount for the gas inflation and, consequently, the volume of the combustion chamber in the body of the gas generator has to be increased to raise the gas temperature and the temperature inside the gas generating unit by combustion of a relatively large amount of gas generating agent since the volume of the combustion chamber in the gas generating unit also has to be increased, it is relatively large and heavy, and this involves such hazards as the possibility of passengers being burnt.
If the gas generating apparatus is reduced in size and weight with a corresponding reduction in the quantity of gas generating agent used therein, the air bag is not inflated to a sufficient extent and its function as a safety apparatus in time of collision is thereby compromised. Therefore, the shortfall in the quantity of gas generated needs to be overcome by supplementing the gas or the like.
For this purpose it is conceivable to incorporate in the gas generating apparatus an air ejector for replenishing air by ejecting a high-pressure gas or a vapor ejector. However, since the primary high pressure gas in these kind of ejector has a pressure as low as 10 kg/cm.sup.2 or less, such an ejector also needs to be relatively increased large in size to be effective when used with such an air bag in a safety apparatus of the type described in order that a sufficient amount of air can be sucked in some tens of milliseconds.
Accordingly, such a gas generating apparatus is inevitably increased in size and weight and this means that it remains impossible for this type of bag to be used as an air bag for an automobile.